Colorimeter



F. J. MA IER COLORIMETER Aug. 13, 1957 2 Sheets-Sheet 1 Filed Feb. 29.19,56

ATTORNEY United States Patent 2,802,391 COLORIMETER Franz J. Maier,Chevy Chase, Md., assignor to the United States of America asrepresented by the Secretary of the Army Application February 29, 1956,Serial No. 568,684

3 Claims. (CI. 88-14) (Granted under Title 35, U. S. Code (1952), see.266) The invention described herein, if patented, may be manufacturedand used by or for the Government for governmental purposes, without thepayment to me of any royalty thereon.

This invention relates to colorimeters. Colorimeters are instrumentsused to compare the absorbing capacity of an unknown (the color of asystem of unknown concentration) with that of a standard (the color of asystem of known concentration or color value). In general and withincertain defined limits, the sensitivity of such visual instruments is afunction of the length of the light path through the colored mediums;the longer this path, the more sensitive the system becomes to slightchanges in the concentrations of the unknowns. Instruments are availableproviding permanent color standards corresponding to definiteconcentrations of substances contained in samples of a large variety ofmaterials. Among such instruments available for the analysis of liquids,those providing the longer light paths are almost invariably moreexpensive than those provided with shorter or smaller tubes. In efforts.to economize, many laboratories are provided with the less expensiveequipment with an attendant sacrifice of accuracy and uniformity ofresults. One purpose of this invention is to provide an instrumentincorporating the accuracy obtainable generally only with those devicesdesigned for the longer tubes combined with the simplicity of housingand construction associated with the less expensive and more generallyavailable laboratory equipment.

The present invention provides an inexpensive, accurate, easily handledcolorimeter which is adaptable for examination of a wide variety ofsolutions, suspensions, etc., by merely changing the tube contents andby substituting, if necessary, appropriate color standards. Theinvention combines Nessler-type tubes, preferably 100 ml. glass tubes,supported in a row in an inexpensive rack of the simplest construction,an attachment providing permanent color standards, an optical systemusable with almost any light source, and means slidably supporting thedial-like attachment and the optical system on said rack, so that theoperator working in the proper light may have a clear view lengthwisethrough any selected one of the row of Nessler-type tubes and mayvisually compare its solution with the permanent color standards, thenmay slide the device along the rack for an examination of the solutionin another tube in the same row. The invention also provides a tube rackattachment which may be removed from one rack and placed on another oflike construction for a different series of examinations. The tubes oneach rack need not be disturbed when the attachment is so removed.

In the accompanying drawings showing a preferred embodiment of theinvention,

Fig. 1 is a perspective view of the complete apparatus;

Fig. 2 is'a vertical central cross section, on a larger scale;

Fig. 3 is an enlarged fragmentary plan view showing the eyepiece, thelight shield, a few of the Nessler tubes and a portion of the rack;

Fig. 4 is a vertical section on line 44 of Fig. 3, onntting the lowerportions of the tubes and rack;

Fig. 5 is a vertical section on line 5-5 of Fig. 3, also omitting mostof the rack;

Fig. 6 is a plan view of the light shield and holder, showing in dottedand full lines the color standards dial directly below;

Fig. 7 is a plan view showing the color standards dial and its support;

Fig. 8 is an enlarged section on line 88 of Fig. 7;

Fig. 9 is a plan view of the holder for the light shield and colorstandards dial;

Fig. 10 is an enlarged (full size) section on line 10-10 of Fig. 4;

Fig. 11 is an enlarged (full size) section on line 11-11 of Fig. 5; and

Fig. 12 is an exploded perspective view showing the elements of theoptical system of Figs. 10 and 11.

Referring particularly to the drawings, the device includes a rack 15for supporting a set of Nessler tubes 16, a reflector 17 for reflectinglight from any convenient light source up through the tubes lengthwise,a sliding support 18 movable along the rack over the upper ends of thetubes, and an optical assembly 19, a light shield 20 and a colorstandards dial 21 all mounted on, but removable from, the slidingsupport. The tube rack 15 supports a mirror or brightly polished metalreflector 17 between its legs 22, 23, said reflector being setpreferably at an angle of about 45 to the horizontal. If preferred,

. the reflector may be mounted on pivot pins to turn about a horizontalaxis and may be clamped by thumbscrews or nuts in the preferred angularposition, so as most effectively to catch the beam of light from thelight source (not shown) and reflect it up through the tubes. Obviouslythe light source may be a window, preferably a north-facing window, orit may be an incandescent lamp or fluorescent tube located at anyconvenient point. The rack has a perforated or apertured shelf 24 forsupporting the lower ends of the Nessler-type tubes and another uppershelf 25 provided with apertures 26 which are large enough to receivethe tubes freely, so that the tubes are easily inserted and withdrawnthrough apertures 26. Light which impinges on the reflector is reflectedthrough apertures 27 in shelf 24 and passes through the tubes and theircontents longitudinally (vertically) to the optical system at the top ofthe rack.

Slidable on upper shelf 25 is a support 18 which straddles the upperends of the tubes as shown in Figs. 1 and 2, having a shape somethinglike an inverted U, with two parallel vertical side plates 28, 29 and ahorizontal top plate 30 secured to the upper edges of the side plates.The side plates 28, 29 are preferably trapezoidal, with their loweredges longer than their upper edges, and on the inside near their loweredges the side plates carry straight ribs or flanges 31, 32 which reston the upper shelf 25 and permit sliding of support 18 thereon. Greaterstability is insured by placing ribs 31, 32 near the lower, wider edgesof side plates 28, 29 and by having the inner surfaces of said platesmake sliding contact with the edges of the shelf 25. Top plate 30 has anaperture 33 for light to pass through from the Nessler-type tube (whosecontents are being examined) to the optical system above. A thin metalring 34 is set in a narrow annular groove cut in top plate 30, as shownin Fig. 8, and color standards dial 21 is supported on the upper edge ofthe metal ring so as to be rotatable manually by the operator. Top plate30 also has a large light aperture 34 and a pair of dowel holes 35 forreceiving dowel pins 36projecting downwardly from the light shield orhood 20, so that the hood is supported on the top plate.

Dowel pins 36 and a raised strip 37 (Figs. 4 and 9). projecting abovethe upper face of the top plate will support the hood firmly yet willpermit easy removal. As Fig.

4-shows,- ,.t:he:hood is spaced slightly fr'omthe rotatable dial 2.1 topermit free turning of the dial Without: rubbing against the: hood.Similar arrangements can be made for supporting permanent color.assemblies.

Hood Zii ispreferably ofv metal finishediin' a. dull black to minimizelight reflections. bottom plate 38, having apertures 39, 4t] and 41,also having apair of sockets'42. (Fig. 6) locatedcentrally for receivingdowel pins 43, 44 on the optical system assembly 19 to-be; described.See Figs. and 10. Hood 2%) is open on one side and closed on the otherthree sides and its side which is opposite the open. side is higher, soas to-shield the eye. of the observer. from the light source, which isbeyond the highside 45..

The. optical system assembly (Figs. 10, 1.1 and 12) includes an eyepiece46, a lens 47, a casing 48, a pair of prisms 49, 50 forming a prismunit, a. panel of clear glass 51, a locking bar 52, and the previouslymentioned pair of dowel pins 43, 44; Said dowel pins are screwthreadedon their inner ends and are passed through perforations in the locking.bar 52 and: are screwed into tapped bores 53, 54 provided in the lowerend of casing 48. This entire optical assembly is available on themarket and per se forms no part of my invention. The prisms 49, 59 aresimilar to the prisms shown in the Bulkley Patent No. 2,684,010. datedJuly 10, 1954, and act in the same Way. Eyepiece 46 and casing 48 may beof black Bakelite or a. similar dark resinous plastic. Lens47 is aweakly magnifying. lens and may be replaced by a more powerful lens bymerely slipping off the frictionally held eyepiece.

The color standards dial 21 is an article of commerce and needs only ageneral description. Other permanent color standard assemblies may be.used in lieu of it. Dial 21 is so supported that one side of it projectsbeyond the sliding support 18, as shown in Fig. 3, so that the operatormay turn it easily. It has a round fiat. shape very much like atelephone dial, is made of Bakelite or similar resinous plastic coloredblack,.andv hastransparent tinted glass or plastic filter disks 64}arranged in a circular series around the center of the dial. Thesefilter disks are accurately made and are of graduated tints andareidentified by insignia such as those shown. at 61 in Fig. 7. Eachinsigne. appears in turn at the aperture 41, Fig. 6, as the dial isrotated, and it identifies. the. filter disk appearing through. aperture49. The insignia illustrated in Fig. 7 are digits running from 0 to 1.6,but could beletters or even symbols; their number is the same as-thenumber of the filter disks which they identify. The upper shelf 25 mayhave labels or stickers (not shown) adhered to it to permit identifyingeach tube on the rack, or the tubes themselves may be identified bylabels in the event their solutions are to be preserved for futurereference. Each of the filter disks is held in its socket 62 by alocking ring 63 andfis removable, hence is replaceable by another filterdisk. If this is done, the insignia will of course be changed tocorrespond. As shown in Fig. 8, the color standards dial has a circularsocket 64 co-axial with the dial, said. socket 64 being open at thebottom to receive the thin circular edge of bearing ring 34. Socket 64is formed by thecentral hub 65 and a ring 66 locked inside the hub (seealso Fig, 7) and spaced therefrom. Ring 66' supports aclear glass disk67 in the exact center of the dial through which light fromv one of thetubes and contents below passes to the optical system located above, asdescribed in theforegoing. It will be clear that the dial 21 may belifted: off its bearing ring 34 by first lifting the shield or hood 2%,and another color standards dial with different filter disks may besubstituted for the one previously in use, or a differently shapedandconstructed color standard holder may be used. Such a substitutionor. changemay. be madewhen changingfrom. one class'of Hood includes: aflat.

solutions to another, e. g., from blood solutions to syrup solutions.

As will now be clear to those skilled in the art, the apparatus of theinvention makes it easy for an operator to get a series of readingsgiving the color values of diiferent solutions or suspension'sina-series of tubes supported in the rack. Each inspection involves twotubes placed side by side in the rack; usually the same solution ordispersion. (the one. to: be examined.) will be. poured intoeach pair oftubes 16, and areagent is thenadded tothe tube that is under the centralaperture 34a. The'sliding support 18 is placed by the-operatoroverthe'pair of tubes to be inspected and with light from the light sourcepassing upwardly through both tubes, one beam of light travels through atube 16 containing: the. solution orv dispersion, thence throughperforation 33, through one of the filter disks as selected by theoperator, and through the optical assembly" 19, while; a second beam oflight after traversing the second. tube (to which. the reagent has been.added') travels.throughperforation 34a, through the clear glass disk 67at the center of thedial, and through the optical system. The. two beamsofv light are brought together because of the prisms 49, 50, and asingle elliptical image which is a composite of the two, will be seen inthe eyepiece. This. is shown in. Fig.3. As one of the pencils of lightpasses through a filter disk, While the other passes through the tubeand its contents then through glass. disk 67, the color of one-half theelliptical image will be a projection. of the particular filter diskthen in the. optical system (as determined by the operator, who rotatesdisk 21) while the color of the other half of the elliptical. image willbe the. color of the tube and its contents. The operator will rotatethedial until he sees that the two-images are of the. same tint or color,then he will make a notation of the reading given by the insigne 61'which then. appears in aperture 41. Other readings are obtainable fromother tubes-by merely sliding support 13 along the rack. As-previouslypointed out, support 18 may be moved to another rack, or a new set oftubes may be placed in theira'ck for. anew set. of readings.v

A number of changes may be. made in the described construction withoutdeparting fromthe invention. Thus the rack could be circular or arcuate,and the slidable support could be adapted to move as freely over such arack. The optical system. does not have to include a mirror or'refiectorin the base of. the rack, since asource of light (such as a fluorescenttube) might be placed in the lower part of'th'e rack, with the.necessary shielding to confine the light emitted. to pencils of lightreaching to tubes and the filter disks prior to entering the opticalsystem; therefore I employ the. term source of. light in its broad senseto include a reflector which acts as a sourcev of light by reflectinglight rays but does not emanate or generate light rays. The optical unitmay be superseded by other units of different construction.

What I claim is:

1. An optical'comparator or colorimeter comprising, in combination; arack for Nessler-type tubes having two horizontal shelves arranged oneabove the other and a pair of legs supporting the shelves; the lowershelf being perforated at intervals to permit light to pass therethroughfrom below and having seats for Nessler-type tubes surrounding saidperforations so that beams of light may pass lengthwise through suchtubes and their contents when such tubes rest on said seats; the uppershelf. having apertures through which such tubes when so seated mayextend; a' support having two light-passing apertures and having meansfixed thereon slidably supporting it on the upper surface of said uppershelf, said support straddling the upper ends of said seated tubes; anoptical assembly carried on said support and including a prism unit forgathering light beams passing through two apertures' in said support,and an eye piece receiving light beams from the prism unit; a colorstandards dial rotatably and removably supported on said support beneathsaid optical assembly but above the light-passing apertures and adaptedto receive two beams of light passing through two adjacent tubes seatedas aforesaid and adapted to transmit said beams to the prism unit and/eye piece of the optical assembly, so that the eye of the operatorplaced at the eye piece may see two images side by side of the contentsof two adjacent tubes seated asaforesaid. 2. The invention defined inclaim 1, wherein the slidable support comprises a perforated upperplate, two side plates fixed at their upper edges to said upper plateand lying in vertical planes, a straight rib fixed to each side plate onthe inside near its lower edge, said ribs together supporting theslidable support by direct sliding contact with the upper surface of theupper self, said slidable support having its side plates extending belowand being substantially in contact with the upper shelf on both sideedges.

3. A portable assembly useful for making color comparisons comprising arigid support having the general shape of an inverted U having two legseach provided with means slidably engageable with a horizontal shelf ofa Nessler tube rack, said support also including a horizontal member towhich the upper ends of the legs are secured; said horizontal memberbeing perforated at two points to permit two generally vertical beams oflight to pass therethrough; a circular color standards dial having acircular series of filter disks of difierent color values and a centraltransparent disk; the distance apart of the perforations in saidhorizontal member being the same as the radial distance between thefilter disks and the central transparent disk; means supporting saidcolor standards dial rotatably and removably on said horizontal member,so that the color standards disks may be moved seriatim over one of saidtwo perforations, the central transparent disk of said dial being abovethe other of said two perforations; and an optical assembly including aneye piece, a lens and light collecting prisms mounted on said supportabove the color standards dial; the entire assembly being movable overthe upper ends of a series of Nessler tubes supported vertically on arack, so that color comparisons may be made of illuminated solutions ordispersions in two adjacent tubes of said series at one time.

References Cited in the file of this patent UNITED STATES PATENTS1,976,672 Peet Oct. 9, 1934 2,007,087 Hird July 2, 1935 FOREIGN PATENTS818,270 Germany Oct. 25, 1951 OTHER REFERENCES Optical Methods ofChemical Analysis by Gibb, Jr., published by McGraw-I-Iill Book 00., NewYork, 1942, pages 131433.

